Hemodynamic data from clinical patient include any patient signal data associated with blood flow and related characteristics, such as blood pressure, blood flow speed, oximetric signal data, etc. Saturation of peripheral oxygen (SPO2) level is an oximetric measurement, which may be non-invasively acquired by optical sensors. Blood pressure (BP) is a mechanical pressure in the blood exerted by circulating blood in blood vessels. There are two types of blood pressure: systolic and diastolic. Both types of blood pressure may be derived either invasively (invasive blood pressure or IBP) or non-invasively (non-invasive blood pressure of NIBP). The systolic blood pressure corresponds to the pressure of the blood when the heart has imparted maximum pressure, while the diastolic blood pressure is the pressure when the heart is in the resting phase.
During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure. The mean BP value decreases as the circulating blood moves away from the heart through arteries, experiences its greatest decrease in small arteries and arterioles, and continues to decrease as the blood moves through the capillaries and back to the heart through veins. The systolic pressure and diastolic pressure signal waveform characteristics (e.g., amplitude, phase, morphology, etc.) may show different kinds of variation due to different cardiac events or arrhythmias. In other words, the mean BP value alone may not be sufficient to differentiate cardiac events based on recognition thresholds. BP is determined by the force and amount of blood pumped, and the size and flexibility of the arteries. Systolic and diastolic arterial BP values are not static, but undergo natural variations from one heartbeat to another and throughout the day (in a circadian rhythm). BP variation may be utilized for monitoring patient healthy status.
Hemodynamic signal data may be used for characterization of cardiac arrhythmias and/or pathological events. Till now, traditional methods of using blood pressure signals focus on stroke volume and cardiac output calculation. Such traditional methods fail to fully capture waveform information from patient blood pressure signal data. In addition, current clinical methods for blood pressure analysis may have different kinds of limitations, such as described in the following.
Current clinical methods utilize only partial hemodynamic information, such as pressure amplitude, time duration, oxygen saturation level, etc. In addition, current hemodynamic diagnostic approaches typically focus on specific parameters, such as systolic-diastolic pressure signal values, without paying attention to the heart rate and cardiac conditions. Some methods purely use amplitude and timing to quantify signal changes, such as maximum amplitude and EoD (end of diastolic)-EoS (end of systolic) timing. During different situations, such as pacing, ablation, asthma, etc., the heart rate and signal strength/shape/latency are not stable, and current diagnostic methods may not be able to efficiently and effectively compare the signals. Further, known methods for blood pressure waveform diagnosis require extensive clinical experience to interpret parameters, calculation accuracy, etc., which may pose a challenge for some users.
Traditional cardiac function analysis typically utilizes electrophysiological signal data (e.g., electrocardiogram or ECG, intracardiac electrogram or ICEG, etc.) for arrhythmia diagnosis. However, electrophysiological signal data are much more easily distorted and affected by electrical noise and bio-artifacts, such as power line noise, patient movement, etc. Hemodynamic signal data may provide better noise immunity and cardiac function analysis stability. Furthermore, there are currently no known sensitive hemodynamic quantitative methods that are well developed for implantable cardiac devices (ICDs). Till now, most ICD instruments still use electrophysiological signal data to monitor, calculate and treat cardiac arrhythmias and pathologies.